Unlike many other recurring enemy extraterrestrial races in science fiction, the Aliens are not an advanced civilization, but predatory creatures with no higher goals than the propagation of their species and the destruction of any life that could pose a threat to them. Like wasps or termites, Aliens are eusocial, with a single fertile Queen breeding a host of subordinate castes. The creatures are known for their potent acidic blood and their pharyngeal jaws, although their biological life cycle, in which their offspring are implanted inside living hosts before erupting violently from their chests, is in many ways their signature aspect. Their design deliberately evokes many sexual images, both male and female, to illustrate a blurring of human sexual dichotomy.

The Alien design is credited to Swiss surrealist and artist H. R. Giger, originating in a lithograph called Necronom IV and refined for the series' first film, Alien.[1] The species' design and life cycle have been extensively added to throughout each subsequent appearance.

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Aliens are primarily solitary ambush predators, although they have been known to adopt swarm tactics when acting in larger groups. Despite their voracious ability to kill, they often seek to take their victims alive to be hosts for more Aliens; victims are taken to the Hive (or simply a secluded location if there is no Hive present), cocooned and immobilized before being impregnated with an Alien embryo.

Continuing advancements made in the field of special effects technology as the series progressed have led to numerous variations in the creature's design, including varying numbers of fingers and limb joints and varying head design.

When standing upright, the Aliens are vaguely bipedal in form, though they adopt a more hunched, quadrupedal stance when walking or sprinting. They have a skeletal, biomechanical appearance and are usually colored in muted shades of black, blue or bronze. Aliens do not radiate heat, as their body heat matches the ambient temperature of the environment in which they are found.[2][3] In most of the films, adult Aliens have the ability of running and crawling along ceilings and walls.[2][4] They have great physical strength, having been shown to be capable of breaking through vent covers and welded steel doors,[2][5] and even of breaking down reinforced pressurised doors.[6]

Aliens have segmented, blade-tipped tails. The sharp tip was initially a small, scorpion-like barb,[7] but from Template:A2 onwards the blade design increased in size and changed in appearance to more closely resemble a slashing weapon.[2][3] From Template:A4 onwards, the tails have a flat ridge of spines at the base of the blade. This was introduced to help them swim convincingly,[5] and was left intact in the subsequent crossovers. The original shooting script for Aliens and the novelization both featured a scene in which Lieutenant Gorman is "stung" by the barb tail and rendered unconscious;[8] in the final cut of the movie, Gorman is instead knocked out by falling crates. As a weapon, the strength of the tail is very effective, having been shown to be strong enough to impale and lift a Predator with seemingly little effort. They are also adept at using their tails as blunt weapons, sometimes to deadly effect, as seen in Template:A1.

They have elongated, cylindrical skulls, but possess no visible facial features other than their mouth, though in the original Alien film, the top of the creature's head was translucent, with a human skull forming the front, including empty eye sockets visible within (although this is hard to distinguish on-screen). This element was re-used for the "Predalien" in Template:AVP2 29 years later. How the creatures see or otherwise rationalise their environment is uncertain. In Template:A3, a fisheye lens was used to illustrate the Alien's point of view. In the novelization of the movie Alien, the creature is held mesmerized by a spinning green light for several minutes. In Aliens, the adult creatures have a more textured head rather than a smooth carapace. In the commentary for Aliens, James Cameron states that this change is a part of the maturation of the creatures, as the creatures in the film had been alive far longer than the original Alien. The smooth design of the carapace would be used again in Alien3 and Alien Resurrection. This design would be kept in Template:AVP1,[9] and abandoned in Aliens vs. Predator: Requiem in favor of the ribbed design. The Aliens' primary weapon is their inner jaw, which is powerful enough to smash through bone and metal.[7][3] On several occasions, Xenomorphs have been seen to suspend those that they kill from the ceiling through unknown means.[7][4]

Throughout their appearances, human-spawned Aliens have been shown to have a fluctuating number of fingers. In Alien, the creature has webbed, six fingered hands. The number of fingers is reduced to three in Aliens, and are shown to be much longer and more skeletal. In Alien Resurrection, the number of digits is increased to four, with two long middle fingers and a pair of thumbs. This design is kept in the Alien vs. Predator films, though the hands were made bulkier in order to make the Aliens seem more formidable against the Predators.[10]

Aliens have been alternately portrayed as both plantigrade and digitigrade organisms, usually in accordance with their host. Human-spawned Aliens were usually portrayed as having humanoid hind limbs, while in Alien3, the featured Alien (which was spawned from a quadrupedal animal) sported double-jointed hind legs due to its quadrupedal host. This characteristic would be continued in Alien Resurrection for the human-spawned Aliens. Tom Woodruff, Jr., who had previously played the "dog-alien" in Alien3, described the human-spawned Aliens in Resurrection as feeling more like a dog than the previous creature, despite having been born from human hosts.[11] The human spawned Alien warriors would revert to a plantigrade posture in Alien vs. Predator.

Xenomorph blood is an extremely potent acid and is capable of corroding on contact almost any substance with alarming speed. It is dull yellowish-green in color, and seems to be pressurized inside the body so that it spurts out when punctured. Shusett suggested the idea that the creature have acid blood as a plausible means to make the creature "unkillable"; given the starship setting, if one were to use traditional firearms or explosives to attack it, its blood would eat through the hull of the ship.[12] In later films in the series, the Aliens are shown to be conscious of the effects of their acidic blood, and even use it to their advantage — in Alien Resurrection, two Aliens escape a cage by killing a third so its acid eats through the cage floor; in Aliens vs. Predator a queen being held by chains apparently instructs several Aliens to slash and cut her, thus corroding the chains.

Alien Drones can produce a thick, strong resin (secreted from their jaws, giving them the look of a slavering beast) that they use to build their Hives and to cocoon their victims. In the original Alien, the Facehugger is shown to be able to "spit" acid, melting the faceplate of Kane's helmet and allowing the creature immediate access to the inside. This ability is also exhibited by adult Aliens in Alien3 and Alien Resurrection; much like a spitting cobra, the creatures use this ability to blind and incapacitate their victims rather than kill them outright.[4][5]

Events at the LV-426colony and on board the USM Auriga showed that the species excels at observational learning and problem solving.[2][5] In both cases, the Aliens managed to learn how to operate the machinery of their mechanized environments at a very basic level. On LV-426, the Aliens were able to cut the power from a section of the complex to allow themselves access to the humans; the Queen was able to learn how to operate an elevator simply by observing it once. The novelization of Aliens notes that the Queen establishing her "nest" at the base's main power plant could equally be the result of her selecting the warmest part of the base to make her nest, or even her deliberately selecting a location where any attackers would be unable to destroy her without destroying the entire facility. In the director's commentary for Aliens, James Cameron noted that the creatures in Aliens had been alive for far longer than the Alien in the first film, and so have had more time to learn how to manipulate the machinery in their environment.[13]

On the USM Auriga, the Aliens were able to use blood from another Alien to melt through their enclosure and escape. The Aliens in the Antarctic temple using a similar strategy to free their Queen from her chains. Furthermore, the creatures can apparently inherit some degree of intelligence, or at least basic instinctual urges, from their host, as seen when a Predalien on BG-386 was witnessed tearing a skull from a human corpse as a trophy, matching common behavior exhibited by the Predator creatures from which the Predalien was spawned.[14] With the exception of the "Newborn", Aliens have demonstrated little actual emotion, save for self-preservation and maternal instincts toward their Eggs and the Queen.

The means by which Aliens communicate amongst themselves is unclear, although it is apparent from their behavior that they possess the ability to do so. While Xenomrophs are able to vocalize a variety of hisses and screeches, it seems probable that the majority of their communication is performed through some other means, possibly involving the use pheromone release or even some form of telepathy. The creatures also possess a unique ability to inherit memories genetically, passed down from one generation to another. These memories go far beyond mere base instinct, and can include recollections of very specific events witnessed by earlier generations.[15] According to Dr. Wren, this purpose of this genetic memory ability is to ensure the species remained intact regardless of "the differing characteristics they might have to adopt from their varied hosts."[16]

Some Dark Horse comics even go so far as to imply that pheromone detection and the scent of their prey's level of fear when confronted determines the behavior and hostility of the xenomorphs during their attacks. According to these stories xenomorphs do very slow, messy and bloody kills when their victim is very scared and has a strong pheromone release due to that condition (Lambert's death in Alien being an example), while cleaner and faster kills take place when the prey do not notice the xenomorphs or is not scared at all of them.

The question of Xenomorph gender is heavily debated. The most widely accepted answer is that Aliens simply have no genders and are completely asexual. This concept has been backed up by the designers of the original creature in Template:A1, who stated that the design deliberately included elements of both male and female sexual imagery in its appearance.[1] The exception to this is the Queen, which due to its role as an egg-layer and general overseer of Xenomorph Hives is usually said to be female, comparable to similar female castes in the insect kingdom. Consequently, some argue that all Aliens are female, given the apparent ability of a typical Alien to molt into a seemingly female Queen. However, as the molting method of Queen creation has never been seen outside of various video games and comics, it remains unclear if this can be considered canon.

Little has been shown regarding the Xenomorph's diet and it remains unclear exactly how they gain sustenance, or if they even require sustenance of traditional means at all. Events in Aliens seem to imply the Xenomorphs do not use humans as a food source, as the Hive is littered with the corpses of colonists used as hosts and yet none of them show any sign of having been consumed, in whole or in part, despite the fact they have apparently been there for some time.[2] Similarly, Template:ACM shows bodies may be left cocooned to the walls of the Hive for as long as 17 weeks without being desecrated or devoured in any way following death.

Conversely, Template:A3 seems to state that Xenomorphs do in fact feed on humans that they kill. The character Golic, who witnesses an attack by the Alien and escapes, subsequently claims that the creature "feeds on minds", although owing to his delusional state it is unclear how accurate this statement is.[4] Later in the film, the Alien is seen apparently feeding on a corpse after a kill, before being distracted by another prisoner.[4] In Template:AVP2, an Alien Warrior is again seen feeding on one of its victims; commentary by the Strausse brothers during this scene mentions that Aliens do feed on humans.[17] The novelizations of the Alien films explicitly state that Xenomorphs feed on humans, sometimes using them as Chestburster hosts first before feeding on their remains afterwards. Xenomorphs on BG-386 were seen to feed occasionally on the humans that they attacked, sometimes while they were still alive,[14]

Xenomorphs operate under a caste system, with groups of specialized individuals performing distinct tasks within the species. It is not clear to what degree these castes are subject to a social hierarchy, although certain Xenomorph types, notably the Praetorians and the Queens, clearly exercise some degree of control and superiority over other more common variations.

While individual Xenomorphs have been known to operate independently, owing to their tendency to reproduce rapidly and in large numbers they are more commonly encountered in groups and often likened to an infestation owing to their tendency to spread and consume all suitable host organisms in an area. As with many other eusocial organisms, Xenomorphs, particularly in larger groups, with create a central nest or Hive in which they will reside, often overseen by an Egg-laying Queen. Raiding parties will be sent out into the surrounding area to search for and capture more hosts, which will then be brought to the Hive and used to create more Xenomorphs. In larger infestations, smaller "satellite" Hives may be created, containing just a few Xenomorphs, allowing victims to be cocooned and impregnated even far away from the Queen herself.[14]

While the origins of the Xenomorphs have never been definitively determined, several notable theories on their beginnings have gained widespread recognition. Perhaps the most prominent of these is that they are not a natural creature, but were created artificially to act as a biological weapon for another, technologically advanced race (a theory supported by Alien director Ridley Scott[18]). Evidence suggested to support this includes the Xenomorph's general bio-mechanical appearance as well as the perceived "perfection" of their physical nature. Various individuals have proposed that the Engineers may be the race that created the Xenomorph, especially given their known propensity for advanced bio-weapons (including the Black Liquid), although another (less widely-accepted) theory is that the Template:Pred may have been responsible, owing to their close and lengthy association with the creatures.[14] To date, no conclusive evidence has been discovered either way.

The Xenomorph life cycle comprises several distinct stages: they begin their lives as an Egg (laid by a Queen), which hatches a parasitoid larval form known as a Facehugger, which in turn "impregnates" a living host host with an embryo known as a "Chestburster". After a gestation period of several hours, the Chestburster erupts violently from the host's chest, resulting in the death of the host.

The Chestburster then matures to an adult phase within a few hours, shedding its skin and replacing its cells with polarized silicon. Due to horizontal gene transfer during the gestation period, the Xenomorph also takes on some of the basic physical attributes of the host from which it was born, allowing the individual Alien to adapt to its host's environment.

File:Queenchamber.pngQueen Aliens are significantly larger and stronger than the basic Warrior, and other casts of Xenomorphs. They are approximately 20 feet tall at the hip and 53 feet in length.[19] Their body structure differs also, having two pairs of arms, one large and one small. The Queen's head is larger than other adult Aliens and is protected by a large, flat crest, like a crown, which can vary from Queen-to-Queen. Unlike other Aliens, the queen also has high heel protrusions from its feet.

Egg-laying Alien Queens possess an immense egg sac attached to their lower torso, similar to the enlarged abdomen of a queen termite. Unlike insect queens, there appears to be no need for drones to fertilize the Xenomorph Queen.[3][5] When attached to its egg sac, the Queen is supported by a "biomechanical throne"[20] that consists of a lattice of struts resembling massive insect legs.

In the initial cut of Template:A1, the Alien possessed a complete life cycle, whereby the still-living bodies of its victims could be converted into new eggs.[21] However, the scene showing this final stage was cut for reasons of pacing, leaving the ultimate origin of the Eggs obscure. This allowed Template:A2 director James Cameron to introduce a concept he had initially conceived for a spec script called Mother,[13] whereby a massive mother Alien laid the Eggs and formed the basis for the Aliens' life cycle. Cameron conceived the Queen as a monstrous analogue to Ripley's own maternal role in the film.[13] In that vein, some critics[22] have compared it to Grendel's mother.[23]

The design of the Queen in Aliens was created by Cameron in collaboration with special effects artist Stan Winston, based upon an initial painting Cameron had done at the start of the project. The Winston Studio created a test foam-core Queen before constructing the full hydraulic puppet which was used for most of the scenes involving the large Alien.[20] In Aliens, Cameron used very selective camera-angles on the Queen, using the "less is more" style of photography.[20] Subsequently the movie won an Oscar for Visual Effects.

An adult Queen reappeared in Template:A4. The original mechanical head previously used in Aliens was provided by Bob Burns. It was repainted with a blend of green and brown, giving it a shimmering, insect-like quality.[10] This color concept would be abandoned in Template:AVP1 in favor of the original black color scheme.[10]

In the climax of the 2004 film Alien vs. Predator, the Queen's basic design was altered to make it more "streamlined" in appearance and its overall size was increased to 6 meters (20 feet) tall. Other changes include the removal of the "high-heel" protrusions on its legs, including additional spines on its head and making its waist thinner because there was no need for puppeteers inside its chest. The animatronic laying queen had 47 points of hydraulic motion.[10] The Queen was also shown more extensively in full, running and fighting, through the use of CGI.

Template:AVP2 introduced a younger form of the full grown Queen, albeit with traits inherited from its Predator host. Recalling the Facehugger's method of embryo implantation, the Predalien uses its inner mouth to directly deposit multiple Chestburster embryos into pregnant female hosts.[24] This is explained by the Brothers Strause as a means of quickly building an army of Aliens before the young queen evolves into its sedentary, Egg-laying state.[25]

The Eggs laid by the Queen are large, ellipsoidal leathery objects between two to three feet high with a four-lobed opening at the top. As a potential host approaches, the egg's lobes unfold like flower petals, and the parasitic Facehugger extracts itself from within and attaches itself to the potential host. Giger initially designed the eggs with a much more obviously vaginal appearance, complete with an "inner and outer vulva".[26] The producers complained that Catholic countries would ban the film if the allusion was too strong, so Giger doubled the lobes to four, so that, in his words, "seen from above, they would form the cross that people in Catholic countries are so fond of looking at."[26]

A facehugger is the second stage in the Alien's life cycle. It has eight long, finger-like legs which allow it to crawl rapidly, and a long tail adapted for making great leaps. These particular appendages give it an appearance somewhat comparable to chelicerate arthropods such as arachnids and horseshoe crabs. The underside of the Facehugger, the part that touches the victim's face, and its orifice (from which extends a proboscis used for delivering alien embryo) is shown in the films only briefly and noticeably resembles a vagina, thus adding to the general sexual look of the Xenomorphs.

The Facehugger is a parasitoid; its only purpose is to make contact with the host's mouth for the implantation process, by gripping its legs around the victim's head and wrapping its tail around the host's neck. Upon making contact, the Facehugger quickly renders the host unconscious — the exact means by which this occurs is unclear. The Facehugger then inserts a proboscis down the host's throat, supplying it with suitable atmosphere[7] whilst simultaneously implanting an embryo. Attempts to remove Facehuggers generally prove fatal,[2] as the parasitoid will respond by tightening its grip and suffocating the host, while the Facehugger's acidic blood prevents it from being safely cut away.[7] Once the Alien embryo is safely implanted, the Facehugger detaches and dies.

Giger's original design for the Facehugger was a much larger creature with eyes and a spring-loaded tail. Later, in response to comments from the filmmakers, Giger reduced the creature's size substantially.[1] At first Giger assumed that the Facehugger would wrap around the outside of Kane's helmet, but Scott decided that it would have far more impact if the Facehugger were revealed once the helmet was removed. Scott and Giger realised that the Facehugger could burn through the helmet's faceplate with its acid blood; subsequent redesigns of the space helmet included a far larger faceplate to allow for this.[27]Dan O'Bannon initially conceived the Facehugger as somewhat resembling an octopus, possessing tentacles. However, when he received H. R. Giger's designs, which substituted tentacles with fingerlike digits, he thought Giger's design concept superior. Since no one was available at the time, special effects creator Roger Dicken created the Facehugger prop himself.[1] The technical elements of the musculature and bone were added by Ron Cobb. Giger's initial design for the smaller Facehugger had the fingers facing forward, but Dicken's redesign shifted the legs to the side. When the foam rubber sculpture of the Facehugger was produced, O'Bannon asked that it should remain unpainted, believing the rubber, which resembled human skin, was more plausible.[28]

In Template:A3, a second type of Facehugger that would specifically carry the embryo of a Queen Alien — dubbed the "Royal Facehugger" — was planned but ultimately dropped.[29] The Royal Facehugger is briefly glimpsed in the extended Assembly Cut of the film, but is not identified as such.[30]

File:Alien-The Chestburster.pngAfter implantation, Facehuggers detach from the host and die. The host subsequently wakes up with no considerable outward negative symptoms. Symptoms build acutely after detachment of the Facehugger, the most common being sore throat, slight nausea, increased congestion and moderate to extreme hunger.[7] In later stages where the incubation period is extended in preparation of a Queen birth, symptoms will include a shortness of breath, exhaustion, and haemorrhaging (detectable through biological scanners and present in nosebleeds or other seemingly random bleeding incidents), as well as chest pains inflicted either in lack of chest space due to the Chestburster's presence, or even premature attempts to escape the host.[4] The incubating embryo takes on some of the host's DNA or traits, such as bipedalism, quadrupedalism[4] or possessing the mandibles of a Predator[3] and other body structure changes. Over the course of 1–24 hours, indeterminable in some cases, and sometimes up to a week in the case of some Queens, the embryo develops into a Chestburster, at which point it emerges, violently ripping open the chest of the host, killing it.

The Chestburster was designed by Template:A1 special effects designer Roger Dicken.[1] Giger had produced a model of a Chestburster that resembled a "degenerate plucked turkey"[31] and was far too large to fit inside a ribcage. Much to Giger's chagrin, his model reduced the production team to fits of laughter on sight.[32] Dicken drafted a series of alternate designs for the Chestburster based on the philosophy of working "back [from the adult] to the child" and ultimately produced "something phallic".[32] The Chestburster in the original Alien was armless but small arms were added in Template:A2 to facilitate the creature crawling its way out of its host's corpse.[33] This concept would be abandoned in Template:A4 and subsequent films. Giger expressed his approval of the design, admitting he would never have been able to produce such a design, due to his phobia of snakes.Template:Citation needed

When a Chestburster erupts from the body of its host, it is less than a foot tall. However, it soon undergoes a dramatic growth spurt, reaching adult size in a matter of hours; in Alien the Chestburster had grown to 2 metres in height by the time the Nostromo crew located it again.[7] The Chestburster is shown to molt before reaching maturity.[7][4] In Template:AVP2 Alien warriors are shown who are still growing, showing shedding skin. In the unrated cut, the Predalien is shown actively wiping off its final molted skin at the film's start. A shed skin of a growing Chestburster is also shown, showing that the creature's final limbs do not grow in the earliest stages.

The Drone is the most basic and common form of Xenomorph found in the Hive; the Drone form acts much like worker bees or ants. The Drones main function is to keep the Hive functioning properly and to gather new hosts for impregnation. They are almost identical to Warriors in appearance with the exception of their smooth, domed skull. Instead of a large blade, their tails end in a stinger-like barb.

The Warrior (also called the Soldier or Hunter) is one of the primary assault castes of the Xenomorph. They are fast, reasonably tough, and savage combatants. Even in death the Warrior is dangerous, as its highly pressurised bloodstream will cause it to burst apart when killed and drench nearby enemies in acid. Warriors have ridged heads, as opposed to the smooth carapace of the Drone, but are otherwise virtually identical; because of this, Warriors are often said to simply be the mature life stage of the Drone, a fact confirmed by James Cameron in his commentary for Template:A2.

The "Runner" (also jokingly referred to as the "Bambi Burster",[29] or "Runner Alien" in the expanded universe), was introduced in Template:A3. The creature itself shares the same basic physical conformation and instincts as the other Aliens shown in the previous films, although there are several differences due to the host it was spawned from (a dog in the theatrical cut, an ox in the Assembly Cut). The Runner Alien in its Chestburster form is a miniature version of the adult, unlike the larva-like human spawned Chestbursters (although the Assembly Cut implies this is the result of the Alien not being able to escape its host at the usual time).[30] The adult is primarily quadrupedal, has digitigrade hind legs and lacks the dorsal tubes of the human-spawned variety. It is also more red-brown in color when compared to other, typically black Xenomorphs.

Praetorians are considerably larger than typical Xenomorphs, but smaller than Queens, and act as guards to the Queen within the Hive. They are easily distinguished by their large head crests, similar to Queens. Some media has also shown them to be capable of molting into a Queen if no Queen is currently present. Praetorians possess much more concentrated acidic blood, and they have been seen to produce a deafening scream that will summon additional Warriors to their aid.

The Jockey-Xenomorph, also known as the Ultra-Morph in Jon Spaihts script, is a Xenomorph born from an Engineer (its name being a reference to the original colloquial name for the Engineers, "Space Jockeys"). The Jockey-Xenomorph is usually depicted as being huge in size. The Jockey-Xenomorph is not to be confused with the Deacon, a creature born from a Trilobite impregnating an Engineer in Template:Pro.

The Predalien is a Xenomorph spawned from a Predator. It is apparently rare and is regarded by the Predators as an abomination and an affront to their species.[14] The Predalien was first depicted in a painting by Dave Dorman and it was subsequently featured in the Aliens versus Predator comics, numerous video games and eventually Template:AVP2.

The Predaliens feature many traits in common with Predators, such as dreadlock-like appendages on their heads, similar mandibles, skin color, and vocalizations. They are large, bulky creatures, and possess greater physical strength than both Predators and human-spawned Xenomorphs. Predaliens also have thicker tails than regular Xenomorphs.

The Predaliens take more after their host than human-spawned Xenomorphs, possibly because the Predator's genes are more potent. This could also explain why many Predaliens have their own unique appearance.

The Cloned Xenomorphs are a mutated Xenomorph breed that were spawned from the Queen that was extracted from the cloned Ellen Ripley, Ripley 8. The cloning process resulted in the Queen and the Drones it spawned becoming subtly altered through the inclusion of human DNA.

While the Cloned Xenomorphs generally resemble normal human-spawned Xenomorphs, they possess several notable differences that make them unique. Their necks are much fleshier compared to the biomechanical neck design seen in normal Xenomrphs, and they display some quadripedal traits akin to the the Runner rather than adopting the mostly bipedal stance of other human-spawned Xenomorphs. There are also differences in the head, which is narrower, with a longer muzzle and more prominent chin. Their tails have a flat ridge of spines at the base of the blade. Additionally, both the Cloned Queen and her Drones were green-brown in color, giving them a shimmering, insect-like quality.

The Newborn, also known as the "Newborn Alien" and "Alien Sapien", was a human-Xenomorph hybrid created when the Queen taken from Ripley 8 developed a second reproductive cycle, based on the human womb. The Newborn is larger than a regular Xenomorph, and notably does not possess the inner jaw of all other Xenomorphs, but instead has a far more humanoid face, including eyes and a nose. Its limbs are long thin, and its skin is soft and flesh-colored.

It possesses immense strength, able to jump huge distances or crush a man's skull with its bare hands. It shared little association with its Xenomorph brethren, going so far as to kill the Queen that bore it, and instead viewed Ripely 8 as its "mother".

The script for the 1979 film Template:A1 was initially drafted by Dan O'Bannon and Ronald Shusett.[1] Dan O'Bannon drafted an opening in which the crew of a mining ship are sent to investigate a mysterious message on an alien planet. He eventually settled on the threat being an alien creature; however, he could not conceive of an interesting way for it to get onto the ship. Inspired after waking from a dream, Shusett said, "I have an idea: the monster screws one of them,"[1] planting its seed in his body, and then bursting out of his chest. Both realized the idea had never been done before, and it subsequently became the core of the film.[1] "This is a movie about alien interspecies rape," O'Bannon said on the documentary Alien Evolution, "That's scary because it hits all of our buttons."[32] O'Bannon felt that the symbolism of "homosexual oral rape" was an effective means of discomforting male viewers.[34]

The title of the film was decided late in the script's development. O'Bannon had quickly dropped the film's original title, Star Beast, but could not think of a name to replace it. "I was running through titles, and they all stank", O'Bannon said in an interview, "when suddenly, that word alien just came out of the typewriter at me. Alien. It's a noun and it's an adjective."[1] The word alien subsequently became the title of the film and, by extension, the name of the creature itself.

Prior to writing the script to Alien, O'Bannon had been working in France for Chilean cult director Alejandro Jodorowsky's planned adaptation of Frank Herbert's classic science-fiction novel Dune. Also hired for the project was Swiss surrealist artist H. R. Giger. Giger showed O'Bannon his nightmarish, monochromatic artwork, which left O'Bannon deeply disturbed. "I had never seen anything that was quite as horrible and at the same time as beautiful as his work," he remembered later.[35] The Dune film collapsed, but O'Bannon would remember Giger when Alien was greenlit, and suggested to director Ridley Scott that he be brought on to design the Alien, saying that if he were to design a monster, it would be truly original.[1]

After O'Bannon handed him a copy of Giger's book Necronomicon, Scott immediately saw the potential for Giger's designs, and chose Necronom IV, a painting Giger completed in 1976, as the basis for the Alien's design, citing its beauty and strong sexual overtones. That the creature could just as easily have been male or female was also a strong factor in the decision to use it. "It could just as easily fuck you before it killed you", said line producer Ivor Powell, "[which] made it all the more disconcerting."[32] Fox was initially wary of allowing Giger onto the project, saying that his works would be too disturbing for audiences, but eventually relented. Giger initially offered to completely design the Alien from scratch, but Scott mandated that he base his work on Necronom IV, saying that to start over from the beginning would be too time-consuming. Giger signed on to design the adult, egg and chest-burster forms, but ultimately also designed the alien planetoid LV-426 and the Space Jockey alien vessel.[1]

Giger conceived the Alien as being vaguely human but a human in full armor, protected from all outside forces. He mandated that the creature have no eyes, because he felt that it made them much more frightening if you could not tell they were looking at you.[32] Giger also gave the Alien's mouth a second inner set of pharyngeal jaws located at the tip of a long, tongue-like proboscis which could extend rapidly for use as a weapon. His design for the creature was heavily influenced by an aesthetic he had created and termed biomechanical, a fusion of the organic and the mechanic.[32] His mock-up of the Alien was created using parts from an old Rolls Royce car, rib bones and the vertebrae from a snake, molded with plasticine. Originally, the creature was to be translucent, but after problems with the fragile see-through suits tearing the idea was scrapped,[36] although the translucent concept was retained for the dome on the creature's skull. The final Alien's animatronic head, which contained 900 moving parts, was designed and constructed by special effects designer Carlo Rambaldi.[1] Giger and Rambaldi would both go on to win the 1980 Academy Award for Visual Effects for their design of the Alien.

Scott decided on the man-in-suit approach for creating the creature onscreen. Initially circus performers were tried, then multiple actors together in the same costume, but neither proved scary. Deciding that the creature would be scarier the closer it appeared to a human, Scott decided that a single, very tall, very thin man be used. Scott was inspired by a photograph of Leni Riefenstahl standing next to a 6'4" (1.94 m) Nubian.[37] The casting director found 7'2" (2.18 m), rail-thin graphic designer Bolaji Badejo in a local pub. Badejo went to tai chi and mime classes to learn how to slow down his movements.[1]

The creature has no specific name, and has been referred to most often onscreen, and in the credits of each film, simply as the Alien. However, the term "Xenomorph" (lit. "alien form" — from the Greek xeno-, meaning "foreign/alien", and -morph, meaning "form") is used by Lieutenant Gorman in Template:A2[2] and by Ellen Ripley in the Assembly Cut of Template:A3.[30] This term has been adopted by fans[38] and used in merchandising[39] as a convenient name for the creature. It is often abbreviated to Xeno, particularly in video games based on the series, where Colonial Marines typically refer to the creatures as such.[14]

Many other oblique terms have been assigned to the Alien. It has been referred to as an organism,[7] a creature,[2] a serpent,[3] a beast,[4] a dragon,[4] a monster,[2] or simply, a thing.[7] The Xenomorphs are also commonly referred to as "bugs" in expanded universe media, especially by Colonial Marines.[14]Ash in Alien even refers to the creature in the film as "Kane's son", after the crew member in whom it incubated.[7] On occasion, specific Aliens have been given more distinct names, such as the main Alien from Template:AVP1, which is listed in the movie's credits as "Grid" after a grid-like wound received during the film,[3] or "Specimen 6" from the video game Template:AVP2010.[14] The species' binomial names are given in Latin as either Internecivusraptus (meant as "murderous thief") in the Alien Quadrilogy DVD or Linguafoedaacheronsis (meant as "foul tongue from Acheron")[40] in some comic books.[41]

In the years since the release of Alien, the Alien has become one of the world's most recognized movie monsters and a pop-cultural icon. In 2003, the Alien was voted as the 14th most memorable screen villain by the American Film Institute.[42]
Blondie co-founder Chris Stein, who is a friend of Giger, pondered in an interview:

I'd like to see someone even vaguely compile how many versions of the Alien are floating around the world in models and stuff; there must be close to 100,000–little toys, things. All the Japanese horror comics just plunder his style.[43]

Examples of Alien-inspired works include the classic video games Contra[44] and Metroid.[45]

The Aliens have appeared in many crossovers (including a large number of intercompany crossovers) in comic books and other media such as novels, toys, and video games. Crossovers include encounters with Terminators, Judge Dredd, Green Lanterns, Batman, and Superman. The largest of these crossovers is the Alien vs. Predator franchise, in which the Aliens battle the Predators. This was an idea that came to comic book artist Chris Warner in early 1989. He and other people at Dark Horse Comics were trying to come up with a good character combo for a new comics series. Dark Horse had been publishing Aliens comic book under license from 20th Century Fox since 1987. In 1990, the first depiction of the idea in film appeared in Predator 2, when an Alien skull, sculpted by Kevin Hudson,[33] appeared as one of the trophies in the Predator spacecraft.

↑"The bellybursters were actually in the first draft that Colin and I read...They had the bellybursters ... caused by an alien warrior, ...We actually made it the Predalien that was reproducing in this fashion"--Greg Strause, "AvP-R: Preparing for War: Development and Production" featurette, from the Aliens vs. Predator: Requiem Region 1 Extreme Unrated Set DVD

↑"Basically the Predalien's kind of a baby queen-there's a phase in between warrior alien and full-blown queen...they do this thing with embryo implantation.. the idea with that was; how does a baby queen quickly form her own little mini-drone army to get the hive built before she evolves into the final state where she can't completely defend herself?"--Colin Strause, "AvP-R: Preparing for War: Development and Production" featurette, from the Aliens vs. Predator: Requiem Region 1 Extreme Unrated Set DVD